1. Field of the Invention
The present invention relates to joints for concrete piles, methods for making concrete pile joints, and methods for joining concrete piles using those joints.
2. Description of Related Art
The most common pile used in many parts of the world, such as in Scandinavian countries, is the pre-cast reinforced concrete pile. Because of manufacturing, structural, transportation, installation, and other limitations associated with concrete piles, the length of the piles is often limited to a pre-determined length. Depending on the situation, it is often necessary to join, or splice, two piles end-to-end at a construction site when an individual pile section is not long enough for a particular application. However, joining discrete concrete piles presents several difficult challenges, such as proper alignment of the pile sections, maintaining continuity of strength, mechanical performance, and other properties. Alignment is critical to prevent slippage, bending stresses, and other problems associated with pile splices.
A concern that is often associated with the use of mechanical splices for piles is the ability of the splice to transmit stress waves of the impact hammer from the upper segment of the pile to the lower segment. A splice with inadequate transmissivity of stress waves would hinder the ability to test the pile for integrity and capacity using the Pile Driving Analyzer (PDA), which is a widely used pile-testing tool in the United States.
A number of solutions have been proposed for splicing reinforced concrete piles. A common method of splicing piles is to provide the ends of the piles to be joined together with four longitudinal locator and locking pins with crosswise holes or grooves that are inserted into the corresponding recesses in the opposing pile ends after the piles have been placed on top of each other in order to be spliced. The pile splice is locked in position by driving locking pins or keys from the side through the crosswise holes or grooves positioned at the corresponding positions at the pile ends. This method of joining piles together has, however, proved to be complicated to manufacture, and it is difficult to make it fit accurately because of the variations in the dimensions of the joint end plates that cover the ends of the piles.
Additionally, a problem with all known pile splices is how to position the joint squarely on top of the pile in connection with casting because they can only be locked to the concrete casting chute at two corners (i.e., the top corners that are visible and accessible). This type of splice varies in detail. However, they all exhibit numerous drawbacks. First, the structure of known joints is complicated, expensive to manufacture and unreliable in service. Second, both the female lock socket and male lock rod must be made of solid steel by machining, which results in considerable wastage of raw material and makes the final product heavy and expensive. Additionally, the lock socket is a closed construction easily penetrated by water, which then freezes at sub-zero temperatures, meaning that pile splicing cannot be carried out under certain conditions. The removal of ice is highly complicated in pile-driving conditions at a construction site. Because of those problems, attempts have also been made to develop a range of joints for splicing reinforced concrete piles together.
U.S. Pat. No. 3,884,589 discloses an exemplary locking joint for concrete piles having joined sections. The facing end surfaces of the sections to be joined are made of metal and have outwardly projecting pins and/or openings arranged therein, the openings communicating with the pin receiving spaces to receive the pin from a next pile section. The pin receiving spaces have metal walls and each pin has a transverse hole therethrough to receive a wedge device to be inserted through the hole in the pin through a bore projecting through the side of the pile section into which the pin is inserted, thereby to hold the ends of the pile sections in firm abutting relationship as previously described. The locking joint is mainly characterized in that the wedge device is held in locking position in the bore and in the transversally extending hole through the pin by locking means located in the bore adjacent the side surface of the pile section and on the wedge device itself.
U.S. Pat. No. 5,032,041 discloses a joining device for concrete piles having a “through-going cavity” (9) that traverses the width of the concrete pile and that allows one to insert a wedge (13) to secure two concrete pile ends together. As shown in FIG. 9 of that patent, the wedge can be easily reversed by driving it back out of the key hole.
U.S. Pat. No. 4,009,550 discloses a concrete pile joint box that is square- or box-shaped, illustrating what many concrete pile joints look like today.
U.S. Pat. No. 3,313,560 discloses a pre-tensioning wire anchoring system for concrete pre-compressed structures (concrete pipes are illustrated), and teaches using a flat socket member adapted to being placed at the end of a concrete form, the socket member having multiple spaced-apart through holes for insertion of a tensioning wire.
EP 1,288,382 discloses a joint for joining reinforced concrete pillars together, and requires that the projecting locking part have an annular groove, a connecting element that includes an annular groove, and a spring-like locking element which locks in the two grooves.
Prior art concrete piles use concrete anchor bars to provide a means to attach and/or align joints. However, anchor bars of that type are not suitable for precision component purposes.
It is not uncommon to observe wet, muddy, and icy conditions at construction sites where concrete piles are used. Because concrete piles are often placed directly on the ground before use at a site, the transverse holes for the locking pins often become clogged with debris, ice, mud, pebbles, etc. However, if a straight path is present to the other side, the debris can simply be pressed through. Ice is a particular concern for concrete piles, as mentioned above, because the spliced sections often become unstable. Therefore, pin-receiving tubes that extend straight through from one side of the pile to the other present a significant prevention in lost resources due to unusable or damages to concrete piles. The aforementioned prior art pile joints and methods of joining piles fail to address those, and other known problems associated with typical concrete piles.